Identification of ETO2-GLIS2 targets by ChIP-sequencing

Acute megakaryoblastic leukemia (AMKL) is a subtype of leukemia primarily diagnosed in childhood and generally associated with poor prognosis. Genetic alterations found in de novo childhood AMKL include the OTT-MAL fusion, MLL and NUP98 fusions and the recently identified ETO2-GLIS2 fusion that involves two transcriptional regulators. In order to identify ETO2-GLIS2-bound regions as well as the chromatin landscape in human AMKL cells, we performed ChIP-seq analyses in AMKL MO7E cell line and in AMKL patient derived cells. Since existing GLIS2 antibodies could not successfully pull-down ETO2-GLIS2, we introduced the GFP at the endogenous GLIS2 loci in the MO7E cell line using a CRISPR/Cas9 approach to obtain physiological expression of a GFP-tagged ETO2-GLIS2 (MO7e-KI cell line). ChIP-seq were performed using antibody against GFP and ETO2 to identify ETO2-GLIS2-bound regions, against ERG to investigate colocalization and against chromatin marks to highlight repressed (H3K27me3) and active (H3K4me3: promoters; H3K27Ac, H3K4me1: enhancers) regions.